Hi, I'm new to boost python and built an extension on Centos 4 64bit using Boost 1.40 and python 2.3.4-14.7.el4_8.2 and it runs like a charm on the same machine. After that I tried to use my extension on a RHEL4 with python 2.3.4-14.3 installed and got the following error: ImportError: /tmp/install/lib/libboost_python.so.1.40.0: undefined symbol: Py_InitModule4 I get the same error when using python 2.6 on Fedora 11 64bit. Is this some kind of versioning issue? I'm quite helpless with this and your help is highly appreciated. Cheers, Jan.